Common Causes of Fever
1. Viral Infections
Viral illnesses are among the most common causes of short-duration fever. Examples include viral upper respiratory infections, influenza, COVID-19, dengue, chikungunya, viral hepatitis and seasonal viral illnesses. Fever may occur with body pain, headache, tiredness, sore throat, cough and runny nose.
2. Respiratory Infections
Fever associated with cough or breathing symptoms may occur with viral respiratory infection, influenza, tonsillitis, pharyngitis, sinusitis, bronchitis, pneumonia, tuberculosis or lung abscess. Fever with significant breathlessness or chest pain requires medical evaluation.
3. Urinary Tract & Kidney Infections
Urinary infections can cause fever, particularly when infection involves the kidneys (pyelonephritis). Symptoms may include burning urination, frequent urination, lower abdominal discomfort, back or flank pain.
4. Dengue, Chikungunya & Malaria
Mosquito-borne diseases are important causes of fever in India. Dengue may present with high fever, severe body pain, headache, pain behind the eyes, nausea and rash. Chikungunya causes fever with prominent joint pain. Malaria produces cyclical fever with chills, rigors, sweating and weakness.
5. Typhoid & Bacterial Infections
Enteric/typhoid fever, staphylococcal, streptococcal, E. coli infections, brucellosis, leptospirosis, rickettsial infections, mycoplasma infections and tuberculosis can all cause fever. Clinical history and exposure details help guide investigation.
6. Tuberculosis
TB is an important consideration in prolonged or unexplained fever. It may involve lungs, lymph nodes, abdomen, bones, kidneys, brain or other organs. Associated symptoms include persistent cough, weight loss, night sweats and tiredness.
7. Autoimmune & Inflammatory Disorders
Fever can occasionally result from non-infectious conditions including rheumatoid arthritis, systemic lupus erythematosus, vasculitis, inflammatory bowel disease, sarcoidosis and other systemic inflammatory disorders.
8. Bloodstream Infection & Sepsis
Severe bacterial infections can spread into the bloodstream and produce sepsis. Warning signs include very high or very low temperature, rapid breathing, low blood pressure, confusion, extreme weakness and reduced urine output. Sepsis is a medical emergency.
9. Drug-Induced Fever
Some medicines may occasionally produce fever. Drug fever may be considered when fever begins after starting a new medicine and no convincing infectious or inflammatory explanation is identified. Never stop a prescribed medicine without medical advice.
⚠️ When Should You Seek Medical Care?
Seek urgent medical attention if you experience any of the following:
- Fever persisting for more than a few days without obvious explanation
- Fever with severe difficulty breathing or falling oxygen saturation
- Fever with altered consciousness, severe confusion or seizures
- Fever with neck stiffness (possible meningitis)
- Fever with unusual bleeding or widespread rash
- Fever with severe abdominal pain or persistent vomiting
- Fever in a very young infant, elderly patient or immunocompromised person
- Fever during pregnancy or during chemotherapy
- Fever with signs of sepsis: low blood pressure, rapid breathing, extreme weakness, reduced urine output
Which Laboratory Tests May Be Considered?
Clinical note: Laboratory tests should be selected by a doctor based on your symptoms, history and clinical examination. Not every person requires all of the tests listed below.
| Test | Why a Doctor May Consider It |
|---|---|
| CBC (Complete Blood Count) | Provides information about white blood cell count, haemoglobin and platelets — supports clinical assessment |
| CRP (C-Reactive Protein) | Marker of inflammation or infection; helps assess severity |
| ESR | Elevated in inflammatory and infectious conditions |
| Peripheral Blood Smear | For suspected malaria or morphological abnormalities |
| Liver Function Tests (LFT) | When liver involvement, hepatitis or jaundice is suspected |
| Kidney Function Tests (KFT) | When renal involvement, dehydration or systemic illness is suspected |
| Urine Routine Examination | To identify urinary tract infection |
| Dengue Testing | When dengue is suspected clinically — test selection depends on day of illness |
| Malaria Testing | When fever occurs with chills, rigors, sweating and relevant exposure |
| Typhoid / Enteric Fever Investigations | When enteric fever is clinically suspected |
| Blood Culture | When bloodstream infection or sepsis is suspected |
| Urine Culture | When urinary infection is suspected, especially with fever and urinary symptoms |
Frequently Asked Questions
Is fever itself a disease?
No. Fever is a symptom and physiological response that can occur with many different illnesses — not a diagnosis in itself.
Does high fever always mean bacterial infection?
No. Viral infections can also produce high fever, while some significant bacterial infections may initially cause only modest temperature elevation.
Can dengue cause fever and low platelets?
Yes. Platelet counts can decrease during dengue infection, but platelet count alone should not be used to determine the severity of dengue.
Can tuberculosis cause prolonged fever?
Yes. TB should be considered among the possible causes of persistent fever, especially when accompanied by prolonged cough, weight loss, night sweats or reduced appetite.
Should everyone with fever undergo the same tests?
No. Investigation should be based on the patient's symptoms, duration of fever, clinical assessment and likely causes. Testing should be targeted rather than ordering everything automatically.
QXL Diagnostic Support
QXL Diagnostics provides laboratory investigations that may assist doctors in evaluating fever when clinically indicated, including routine haematology, biochemistry, inflammatory markers, microbiology and selected infectious disease testing. Laboratory tests support clinical diagnosis — they do not replace consultation with a qualified healthcare professional.
Related Health Topics
Medical Review
Medically reviewed by: Dr. Shantakumar Muruda, MD - Medical Biochemistry; Founder & CEO, QXL Diagnostics Super Speciality Lab, Bengaluru
Last medically reviewed: 2026-09-11
Clinical reference framework:Harrison's Principles of Internal Medicine; Tietz Fundamentals of Clinical Chemistry and Molecular Diagnostics; and relevant specialty guidance as clinically appropriate.
Medical Disclaimer: This information is intended for general health education and does not diagnose an individual medical condition. It does not replace consultation, diagnosis or treatment by a qualified healthcare professional. Seek urgent medical attention for severe, sudden or rapidly worsening symptoms or any emergency warning signs described above.